The fates of two Islamic State hostages -- a Japanese journalist and a Jordanian air force pilot -- remained unknown Friday, a day after the latest deadline passed for a prisoner swap.

Jordan's military said officials were working non-stop on the case of pilot Mu'ath al-Kasaesbeh, who was captured after his jet crashed in Syria last month.

Islamic State militants had threatened to kill him if Jordan did not release Iraqi prisoner Sajida al-Rishawi by sunset Thursday. Al-Rishawi is on death row in Jordan for her role in a deadly 2005 bombing in Amman. But Jordan said it would only release her with proof its pilot is alive.

People in both Jordan and Japan took to the streets Friday to call for the hostages' safe return.

IS threat

A recorded voice warning of the threat to the Jordanian pilot was purported to be that of Japanese hostage Kenji Goto. Goto's wife, Rinko, issued an emotional appeal late Thursday to both Tokyo and Amman to save her husband's life. But the audio recording, apparently released by the Islamic State, did not promise that either of the hostages would be released in exchange for al-Rishawi.

Al-Kasaesbeh is believed to have been captured after his jet crashed in Syria last month during a bombing mission against Islamic State, which has seized large parts of Syria and Iraq. He is from an important Jordanian tribe that strongly supports the country's ruling Hashemite monarchy.

Polls have shown there is opposition in Jordan to the country's involvement in the U.S.-led coalition fighting Islamic State.

Last week, Islamic State released a video showing Goto holding pictures of another Japanese hostage, Haruna Yukawa, apparently beheaded. In the video, a man's voice, identifying himself as Goto, directly addresses Japanese Prime Minister Shinzo Abe, accusing him of responsibility for Yukawa's death.

Goto is believed to have been captured by Islamic State last year while trying to rescue Yukawa.

Abe, while on a recent tour of the Middle East, announced $200 million in non-military aid for countries fighting Islamic State militants.

The Islamic State group threatened last week to behead the Japanese hostages unless it received a $200 million ransom. The demand for money has not been repeated in recent statements.